1. Field of the Invention
This invention relates generally to optical wireless communication links, and more particularly, to a method of synchronizing servo timing in an optical wireless link (OWL).
2. Description of the Prior Art
An optical wireless link system consists of two stations: Each of which contains an optical transmitter and an optical receiver. The transmitter is able to change the direction of its transmitted beam by known amounts of angular displacement. The receiver sees this motion and sends position correction information back to the transmitter. This feedback is used by a servo control loop to position the transmitted beam on the receiver of the remote station.
While both OWL's have roughly equal sample periods, their servo systems generally operate in an asynchronous mode from one another. This asynchronous operating mode however, is not always an optimal configuration. When a position feedback packet is received by a first OWL, for example, some processing is required to identify the packet as a position feedback packet, and then proceed to process the position feedback information for control use. The first OWL's data processor also has other periodic tasks, such as sampling its own position detectors, and preparing related data for transmission to the second OWL. If the incoming packet is aligned in time with the sampling and transmission of the local position, a delay will occur in the feedback loop as one task waits on completion of the other. This delay can have adverse implications on the control system, such as, for example, decreasing the phase margin.
In view of the foregoing, it would be desirable and advantageous in the optical wireless communication art to provide a technique that synchronizes servo timing in an optical wireless communication link.